package com.atguigu.java;

import org.junit.Test;

import java.io.*;

/**
 * @author yihu
 * @create 2021-06-01 17:01
 * @email:1057202547@qq.com
 * @dec:
 * 处理流之一：缓冲流的使用
 *  1.缓冲流：
 *  * BufferedInputStream
 *  * BufferedOutputStream
 *  * BufferedReader
 *  * BufferedWriter
 *  *
 *  * 2.作用：提供流的读取、写入的速度
 *  *   提高读写速度的原因：内部提供了一个缓冲区
 *  *
 *  * 3. 处理流，就是“套接”在已有的流的基础上。
 *
 */
public class BufferedTest {
    @Test
    public  void BufferedStreamTest() {
        BufferedInputStream bis = null;
        BufferedOutputStream bos = null;
        try {
            File srcFile = new File("snipaste_20200617_145159.png");
            File desFile = new File(System.currentTimeMillis() +".png");
            //创建流
            //--2.1 造节点流
            FileInputStream fis = new FileInputStream(srcFile);
            FileOutputStream fos = new FileOutputStream(desFile);
            //--2.2 造缓冲流
            bis = new BufferedInputStream(fis);
            bos = new BufferedOutputStream(fos);
            //读写
            byte[] buffter = new byte[5];
            int len;
            while ((len = bis.read(buffter))!=-1){
                bos.write(buffter,0,len);
                // bos.flush();//刷新缓冲区
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            //关闭流 要求：先关闭外层的流，再关闭内层的流
            //关闭外层流的同时，内层流也会自动的进行关闭。关于内层流的关闭，我们可以省略.
            try {
                if(bos!=null)
                  bos.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
            try {
                if(bis!=null)
                  bis.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    //实现文件复制的方法
    public void copyFileWithBuffered(String srcPath,String destPath){
        BufferedInputStream bis = null;
        BufferedOutputStream bos = null;

        try {
            //1.造文件
            File srcFile = new File(srcPath);
            File destFile = new File(destPath);
            //2.造流
            //2.1 造节点流
            FileInputStream fis = new FileInputStream((srcFile));
            FileOutputStream fos = new FileOutputStream(destFile);
            //2.2 造缓冲流
            bis = new BufferedInputStream(fis);
            bos = new BufferedOutputStream(fos);

            //3.复制的细节：读取、写入
            byte[] buffer = new byte[1024];
            int len;
            while((len = bis.read(buffer)) != -1){
                bos.write(buffer,0,len);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            //4.资源关闭
            //要求：先关闭外层的流，再关闭内层的流
            if(bos != null){
                try {
                    bos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(bis != null){
                try {
                    bis.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            //说明：关闭外层流的同时，内层流也会自动的进行关闭。关于内层流的关闭，我们可以省略.
    //        fos.close();
    //        fis.close();
        }
    }

    /*
        使用BufferedReader和BufferedWriter实现文本文件的复制
    */
    @Test
    public void testBufferedReaderBufferedWriter(){

        BufferedReader br = null;
        BufferedWriter bw = null;
        try {
            br = new BufferedReader(new FileReader(new File("bufffile.txt")));
            bw = new BufferedWriter(new FileWriter(new File("bufffilecopy.txt")));

            //读写
            char[] cbuffer = new char[1024];
            int len;
            while ((len = br.read(cbuffer))!=-1){
                bw.write(cbuffer,0,len);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if(br != null){
                try {
                    br.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(bw != null){
                try {
                    bw.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }



    }

    @Test
    public void testCopyFileWithBuffered(){
        long start = System.currentTimeMillis();
        String srcPath = "C:\\Users\\yihu\\Desktop\\test.mp4";
        String destPath = "C:\\Users\\yihu\\Desktop\\test3.mp4";
        copyFileWithBuffered(srcPath,destPath);
        long end = System.currentTimeMillis();
        System.out.println("复制操作花费的时间为：" + (end - start));//34--->12
    }

}
